Runes in good hands.

Author, in which part of White Forest are the mushrooms located? I can't seem to find them.

Well, how to explain... You enter the White Forest, go up, right, then down and left, and keep going until you see a mountain. They are scattered near it.

Added 1 minute ago

How to solve the Druid's puzzle?

Quickly. The answer is in the attached material. I can personally send you the solution if you're interested.